body nav {
  width: 1000px;
  height: 60px;
  margin: 20px auto;
  background-color: white;
  padding: 20px;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

body nav .left {
  width: 100px;
  height: 100%;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

body nav .left .arrow {
  width: 15px;
  height: 15px;
  border-bottom: 2px solid black;
  border-left: 2px solid black;
  transform: rotate(45deg);
}

body nav .left span {
  font-size: 14px;
}

body nav .center {
  font-size: 20px;
}

body nav select {
  outline: none;
  border-radius: 5px;
  width: 100px;
  height: 30px;
  background-color: #009933;
  box-shadow: none;
  font-size: 14px;
  color: #ffffff;
}

body nav select option {
  background-color: #dddada;
  color: #666;
}

body main {
  width: 1000px;
  display: flex;
  flex-wrap: wrap;
  margin: 0 auto;
}

body main > .box {
  margin-right: 15px;
  margin-left: 16px;
  margin-bottom: 30px;
  width: 300px;
  background-color: white;
  border-top-right-radius: 10px;
  border-top-left-radius: 10px;
}

body main > .box .title {
  width: 100%;
  height: 40px;
  line-height: 40px;
  color: #333;
  font-size: 15px;
  border-bottom: 1px solid #d6d6d6;
  padding-left: 15px;
  padding-right: 15px;
}

body main > .box .title span {
  font-size: 14px;
  color: #666;
}

body main > .box .title span:nth-child(2) {
  color: red;
}

body main > .box .join {
  width: 100%;
  height: 40px;
  background-color: green;
  color: white;
  border: 0px;
}

body main > .box .joinin {
  width: 100%;
  height: 40px;
  background-color: #cccccc;
  color: white;
  border: 0px;
}
